Adani Group is facing growing pressure to reveal which company in its complex corporate web has applied for a $1 billion subsided loan from the Australian Government, amid fears money could be shifted to a tax haven and investors may have been misled.

An Australian law firm has written to the Bombay Stock Exchange asking it to clear up the confusion about a $1 billion funding application to the Federal Government's Northern Australia Infrastructure Facility (NAIF).

The loan would finance a 400-kilometre railway from Queensland's Abbot Point Coal Terminal to a planned massive mine in the Galilee Basin, which, if it goes ahead as proposed, would contain six open-cut pits and five underground collieries.

The NAIF has refused repeated requests from the ABC for information about which Adani entity has applied for the funding.

Each request has received this standard form response:

"NAIF has an independent board whose members are committed to meeting NAIF's obligations to maintain the confidentiality of its dealings. It will also comply with its statutory obligations in relation to the organisation's public reporting requirements."